1. Field of the Invention
The invention relates to a method and an apparatus for producing fibers from thermoplastic materials, in particular from glass fibers.
2. Background of the Related Art
When carrving out this such method (as disclosed in DOS No. 28 49 357), not only is there a need for consistent quality in the glass fiber products produced but also the manufacturing costs are of considerable importance. Since such a method is carried out at relatively high temperatures, the fibring apparatus used is exposed to particularly high stresses which affect the effective life of its centrifugal ring. The life of the centrifugal ring is also influenced by the fact that during operation the peripheral wall of the centrifugal ring may bulge out and thus pass into the hot gas flow, which means that this bulged-out wall part is exposed to particularly high temperature stresses.
Furthermore, in the case of an interruption in production during which the supply of molten material to the centrifugal ring is interrupted by an interposition of what is referred to as a frit channel, and the cooling effect of the molten material is no longer applicable, the centrifugal ring is entirely exposed in a flow of gas which is heated to more than 1400.degree. C., which then can lead to a harmful over-heating of the centrifugal ring unless the temperature of the gas flow is rapidly reduced. It is possible, if there is an interruotion in production, to limit any increase in temperature at the peripheral wall of the centrifugal ring by manually measuring the temperature of the peripheral wall by means of a pyrometer and in consequence manually reducing the temperature of the gas flow. However, this represents an unsatisfactory management of temperature and does not reliably exclude the possibility of the centrifugal ring becoming overheated or being exposed to a shock cooling.
It is also known to determine the temperature of the gas flow by use of a thermo-element provided in the combustion chamber of the air-gas mixture, however, this technique only indicates a reference temperature, which is not necessarily proportional to the temperature of the cen.trifugal ring, so that it is not well suited for managing the temperature of the centrifugal ring.